B s Oscillations and Rare Decays at the Tevatron

1

Ralf BernhardUniversity of Freiburg

Ralf BernhardUniversity of Freiburg

28. April 2008 Ralf Bernhard

GDR SUSY Workshop28. April 2008 Strasbourg

Bs Oscillations and Rare Decays at the Tevatron

Bs Oscillations and Rare Decays at the Tevatron

2

Outline

Motivation Measurement of Bs

mixing: ms

Measurement of CP Violation in the Bs

system Rare leptonic decays b->llX transitions Summary

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.



3

Motivation

Why B Physics? - It’s got it all! Electroweak symmetry breaking determines

flavor structure: CKM matrix, CP violation, FCNC’s QCD Modeling: production, spectroscopy, masses,

lifetimes, decays Challenges lattice gauge, Heavy Quark Effective Theory, strong symmetries

Search for new physics rare decays and

Why at the Tevatron?

Complementary to (4S) B factories

QuickTime™ and aTIFF (LZW) decompressor




Why huge matter-antimatter

asymmetryin the universe?

Why huge matter-antimatter

asymmetryin the universe?

4

Tevatron



Tevatron continues to perform well Over 3.9fb-1 delivered and 3.4fb-1

recorded by each experiment, 2.8fb-1 analysed

Peak luminosities of ~3 x1032 cm-2 s-1 up to 10 interactions

5

Detectors

Relevant for B physics:DØ Tracker: excellent coverage

& vertexingSilicon & scintillating fiber Small radii, but extending to || < 2 New Layer 0 silicon on beam pipe in 2006, improving impact para. resol. Triggered muon coverage: || < 2 E.g.triggers: dimuons, single muons, track displacement @ L2

CDF Tracker: excellent mass resolution & vertexingSilicon, Layer 00Large radii drift chamber, many hits, excellent momentum resolutiondE/dx (and TOF): particle idTriggered muon coverage: || < 1E.g.triggers: dimuons, lepton + displ. track, two displaced tracks

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Mixing and Oscillations



7






8






Whole new window for New physics

Very sensitive for NP

Sensitive for NP

Not sensitive for NP

Probe entire matrix

9

Frequency of Oscillations



Decays:

10

Decay channels



11

CDF Signal Selection



12

DØ Signal Selection



RunIIa





Only 250 reconstructed and tagged hadronic events (CDF ~500)

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Decay channels



14

Amplitude scan

tmAAPtmmP sss ±≈⇒±≈ cos1)(cos1)(

1/m

m

time

frequency

Asymmetry

Power spectrum

Motivation is to simplify combining results with other

experiments



15

Bs: ms, Frequency of Osci.









16

CP Violation



In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!

e.g. 43 in MSSM e.g. 43 in MSSM

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CP Violation






18

CP Violation






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Bs: ms, Frequency of Osci



TevtronB Factories

Not much room for New Physics!

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First assume no CP violation in Bs mixing,

s=0


s=0

Measurement of Bs→Ds

(*)Ds(*)

Three channels [DsDs (PP), Ds*Ds (VP), Ds*Ds* (VV)]

Heavy quark limit + factorization Bs

odd→Ds*Ds is forbidden

Ds*Ds* in S-wave Ds(*)Ds(*) pure CP even

Flavor specific Bs lifetime Flavor specific decays carry equal amounts of BH and BL

Get flavor specific lifetime if FS data with is fit w/ single exponential

Bs→J/ P → VV Even and odd paths distinguishable with angular analysis of final

state particles

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠

⎞⎜⎝

⎛

Ο+⎟⎠

⎞⎜⎝

⎛

=→ 1

2)( (*)(*) CP

sss DDBBF

CP and mass eigenstates are the same

21

from Bs→Ds(*)Ds

(*)

Trigger on muon from semileptonic Ds decay Ignore any photons Look for correlated production of Ds→and Ds→

Bs Ds

Ds

1

Phy

. Rev

.Let

ters

99,

241

801

(200

7)

22

from Bs→Ds(*)Ds

(*)

Bs Ds

Ds

1

031.0038.0030.0035.0

016.0019.0015.0017.0

(*)(*)

079.0

039.0)(

++−−

++−−

=

=→

CP

sss DDBBF

Phy

. Rev

.Let

ters

99,

241

801

(200

7)

23

Bs Flavor Specific Lifetime

psBsFS052.0046.0055.0381.1)( +

−±=τ

Phy

s.R

ev.L

ett.

97:2

418

01,2

006

Ds→D+→

hep-

ph/0

2010

71

Know flavor at time of decay from charge of decay product

50% CP-even, 50% CP-odd at time t0

+-

24

Bs Flavor Specific Lifetime



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Bs→J/

Heavy (H, CP-odd) and Light (L, CP-even) Bs states

Decays into two vector mesons that areeither CP-odd (L=1) or CP-even (L=0,2)

Time-dependent angular distributions allow separation of components

Simultaneous fit to lifetime and three angles





Not “flavor specific”,predicted to be moreCP even than odd

26



Bs→J/

odd / heavy

even / light

1976±65 Candidate BS

arXiv:/0802.2255



arXiv:/:0712.2348

2506±51



27

and s




s=0


s=0CP and mass eigenstates are the same

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CP Violation






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CP Violation in Bs System






Explore new part of matrixExplore new part of matrix

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Explore new part of matrixExplore new part of matrix

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How could New Physics affect these phases

Both CDF and DØ measure/observe the phase responsible for CP violation in Bs -> J/ decays

Use flavor tagging to identify initial flavor of Bs or Anti Bs in J/ decays (and know value of ms)





32

CP Violation in Bs→J/ Even without initial state flavor tagging, have

sensitivity to s

But 4-fold ambiguity, reduce to 2-fold with flavor tagging...



33

CP Violation in Bs→J/







Now use initial state flavor tagging

Ambiguities

34



CP Violation in Bs→J/

Now using initial state flavor tagging, constrain strong phases

Ambiguities



35

s Measurement

In Standard Model: s≈arg(-Vts) ≈ 0.004 rad.In Standard Model: s≈arg(-Vts) ≈ 0.004 rad.

Observables: Semileptonic asymmetries, interference in decays to CP eigenstates

A. L

enz,

U. N

iers

te h

ep-p

h/06

1216

7

Bs

Ds

Bs

Bs

Ds

Bs

B

B ↕ this versus this ↕

Two samples

Exclusive untagged Ds

Inclusive like-sign

φ

tan)()()(

)()(

muntaggedA

DNDN

DNDNSL

ss

ss

Δ

ΔΓ≈=

+

−−+

−+

φ

tan)()()(

)()(

muntaggedA

DNDN

DNDNSL

ss

ss

Δ

ΔΓ≈=

+

−−+

−+

)(2)()()(

)()(untaggedAtaggedA

NN

NNSLSL ==

+−

−−++

−−++

)(2)()()(


NN

NNSLSL ==

+−

−−++

−−++

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Same sign Dimuons

0032.00044.00092.0 ±±−=SLA

)()( sSLdd

ssdSLSL BA

Zf

ZfBAA +=

N(same sign) ≈ 310K

0101.00064.0),( ±−=sSL BA

Z ~ 2

Phy

s. R

ev. D

74,

092

001

(200

6)

~60/40 mix of Bd and Bs

ASL(Bd)=-0.0047±0.0046 (HFAG, B-factories )

)(2)()()(


NN

NNSLSL ==

+−

−−++

−−++

Regular flipping of polarity of solenoid (tracking) and toroid (muons) magnets essential for controlling systematic uncertainties

37

Exclusive Bs→Ds±Results

€

ASL (Bs,Dsμ) =

0.0245 ± 0.0193± 0.0035

€

ASL (Bs,Dsμ) =

0.0245 ± 0.0193± 0.0035

0090.00001.0

),(

±=+ ssSL DBA

0090.00001.0

),(

±=+ ssSL DBA

Exclusive Ds

m()

pol

pol

DØ Combined:

116.002.0tan −±=⋅ psss φUsing ms from CDF:

Phy

s. R

ev. L

ett.

98, 1

5180

1 (2

007)

φ

tan)()()(

)()(

muntaggedA

DNDN

DNDNSL

ss

ss

Δ

ΔΓ≈=

+

−−+

−+

φ

tan)()()(

)()(

muntaggedA

DNDN

DNDNSL

ss

ss

Δ

ΔΓ≈=

+

−−+

−+

CDF: 1.6 fb-1, CDF Note 9015CDF: 1.6 fb-1, CDF Note 9015QuickTime™ and a

TIFF (LZW) decompressorare needed to see this picture.

38

s Results



Combined with older DØ analysis before flavor tagging

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CP Violation in Bs: Combination

In Bs→J/ flavor-tagged analyses, in (s,s) space CDF has ~1.5 deviation from SM, DØ ~1.8 deviation, consistent with each other

Need to be careful, non-parabolic log(L), multiple correlations (best is simply more data!!)

DØ, 2.8fb-1

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UTfit results



Next talk from Marcella Bona

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Direct CP violation in b Hadrons

Direct (not through mixing) CP violation expected to be large in some b hadron decays, including B mesons and b Baryons

Measure asymmetry: f=final state

CDF: Br's and asymmetries of two-body charmless states, Bhh’

Expectations, asymmetry ~30% First CP asymmetry measurement

in b baryon decays







42



Direct CP violation in b Hadrons

DØ: Small (~1%) CP asymmetry expected in SM for B+→J/K+

Again, frequent solenoid and toroid polarity reversals essential to control charge asymmetry systematic uncertainties

Correct for K+/K- asymmetry <1% precision factor ~2

better than current world average



Accepted by Phys. Rev. Lett.

43

Purely leptonic B decay

B->l+ l- decay is helicity suppressed FCNC SM: BR(Bs->) ~ 3.410-9

depends only on one SM operator in effective Hamiltonian, hadronic uncertainties small

Bd relative to Bs suppressed by |Vtd/Vts|2 ~ 0.04 if no additional sources of flavor violation

reaching SM sensitivity: present limit for Bs -> +- comes closest to SM value

SM expectations: Current published limits at 95%CL:

Br(Bdl+l-) Br(Bsl+l-)

l = e 3.4 × 10-15 8.0 × 10-14

l=μ 1.0 × 10-10 3.4 × 10-9

l=τ 3.1 × 10-8 7.4 × 10-7

Br(Bdl+l-) Br(Bsl+l-)

l = e < 6.1 ·10-8 < 5.4 ·10-5

l=μ < 1.8 ·10-8 <5.8 x 10-8

l=τ < 2.5% < 5.0%

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Purely leptonic B decay excellent probe for many new

physics models particularly sensitive to models

w/ extended Higgs sector BR grows ~tan6 in MSSM 2HDM models ~ tan4 mSUGRA: BR enhancement

correlated with shift of (g-2)

also, testing ground for minimal SO(10) GUT models Rp violating models,

contributions at tree level (neutralino) dark matter …

Two-Higgs Doublet models:Two-Higgs Doublet models:

Rp violating:Rp violating:


are needed to see this picture.?

45

Search Strategy

Preselection of Di Muon events Normalization channel B+→J/ψK+

Background estimation using sidebands

Background reduction using a LHR (DØ) or NN (CDF)

0.8 ± 0.2 eventsObserve 1 event

NN

RunIIa

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Limits

Relative NormalizationB+ /Bs relative efficiency of normalization to signal channelfs/fu fragmentation ratio - use world average (3.71) with 15%

uncertaintyBd /Bs relative efficiency for Bd-> versus Bs-> events in

Bs search channel (~0.95) R = BR(Bd)/BR(Bs) is small due to |Vtd/Vts|^2

Br(Bs-> 2 fb-1 7.3×10-8 Prelim.DØ

Br(Bs-> 2 fb-1 4.7×10-7 Prelim.CDF

Br(Bs-> combined 3.6×10-8 HFAG

at 90% CL

DØ Note 5344

PRL 100,101802 (2008)

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Rare decays constraining NP



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Study of b -> s l+l-

long-term goal: investigate b -> s l+ l- FCNC transitions in B+, Bd and Bs mesons

B+ -> l+ l- K+ and Bd -> l+ l- K* established at B factories Bs -> l+ l- only accessible at the Tevatron

SM prediction: short distance BR: ~1.6×10-6 About 30% uncertainty due to B-> form factor

2HDM: enhancement possible, depending on parameters for tan and MH+

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b->sl+l- Theory

The forward backward asymmetry

is defined as the asymmetry between

forward and backward emitted

positive leptons in the dilepton rest frame

where the direction is relative to the

direction of the B meson.

The forward backward asymmetry

is defined as the asymmetry between

forward and backward emitted

positive leptons in the dilepton rest frame

where the direction is relative to the

direction of the B meson.

Mass spectrum Mass spectrum

Sensitive to “newPhysics” contribution

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B->h @ CDF





arXiv:0804.3908

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Branching ratio overview



Need more statistics to measure charge asymmetry vs. invariant di-lepton mass and to add Bs channel! Need more statistics to measure charge asymmetry vs. invariant di-lepton mass and to add Bs channel!

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Summary

ms established and well measured at the Tevatron

Bs system and CP studies opening a powerful new window: possibly already providing hints of new phenomena?

Limit on rare decay Bs->is getting more and more stringent, help constrain physics beyond the SM

Other FCNC (b-> sll) decays test the SMTevatron doing very well, expect to at

least double our data-set by the end of running

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Back up slides

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Pre-Selection

Cut on Mass region of di-muon sample 4.5 < m < 7 GeV/c2

Two medium muons with a net charge of zero and a pT greater than 2.5 GeV

The triggered muons have reconstructed tracks in the tracker with at least 3 hits in the Silicon tracker at least 4 hits in the Fiber tracker

Good reconstructed vertex (cut) Cut on the uncertainty of the transverse decay

length (Lxy) < 150 m A minimum pT of the Bs candidate of 5 GeV is

required

55

Normalization

Additional cuts on the Kaon and B candidate are: Kaon pT > 0.9 GeV/c Collinearity of > 0.9 is required 2 of the vertex fit contribution not more than 10, together < 20 Also cut on the LHR cut like the Bs->signal

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Likelihood

RunIIa

RunIIb

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Systematic Uncertainties

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Bs→J/

Time evolution: even plus odd components

t

t

oddeven

H

L

eoddtf

eeventf

CPCAA

tAtAt

−

−

≈

≈

+

+≈

),(

),(

)(

),,,(),,,()(*

θθCP conserving interference

CP states = heavy, light states

Time evolution: pure even case

t

even

Leeventf

tAt−≈

≈

),(

),,,()( θ

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ts

ts

ts

ts

stt

oddeven

LH

HL

HL

eeoddtf

eeeventf

eeCPVAA

CPCAA

tAtAt

−−

−−

−−

−++≈

−++≈

−+

+

+≈

)cos1()cos1(),(

)cos1()cos1(),(

sin))((

)(

),,,(),,,()(

*

*

φφ

φφ

φ

θθ

Bs→J/

Time evolution: even plus odd plus CPV

CP conserving interference

Heavy and light states are mixed CP

CP violating interference between two paths

Time dependent angular analysis of untagged sample

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Combined (coss≡1)

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Bs→J/Results

(ps-1)

τ(ps)

(ps-1)

s(rad)

log(L) = 1

Likelihood invariant to simultaneous flip of sign of

and even-odd strong phase difference 4-fold ambiguity

14.001.0

1

56.079.0

02.009.017.0+−

−

±−=

±±=

s

s ps

φ

Phy

s. R

ev. L

ett.

98, 1

2180

1 (2

007)

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Bs→J/ angles

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Flavor Specific Bs Lifetime

( )LHss BBDB +=→2

1μν

( )LHFS ttt eee τττ ///

2

1 −−− +≡

Flavor specific decays carry equal amounts of BH and BL

Get the flavor specific lifetime when you fit FS data with single

exponential

Maps out a 2-D constraint on the average width and the width

difference

=

⎟⎟⎠

⎞⎜⎜⎝

⎛

−+

=

2

1

112

2

y

y

y

sFSτ

hep-ph/0201071

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Bs Semileptonic Sample

Ds→D+→

+

K+

KBs Candidate

SVPV

Charge correlation to isolate Bs sample

Transverse decay length determined in lab frame

Boost back using MC to estimate neutrino momentum

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Bs→J/ P →VV

Even and odd paths distinguishable with angular analysis of final state particles

A0 A||

Even waves

A┴

Odd waves

Proper time

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Bs→J/

1039±45 Bs Candidates

Flight length significance > 5

B s Oscillations and Rare Decays at the Tevatron

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